基于DSP的汽车磁流变减振悬架系统控制策略设计与研究外文文献.doc

基于DSP的汽车磁流变减振悬架系统控制策略设计与研究外文文献.doc

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RUCKSUSPENSIONSYSTEMOPTIMIZATION

INTRODUCTION

Trucksuspensionsystems,hardwareinnovationsforimprovements,analyticalinvestigationstoimprovedesign,techniquesfortesting,andcomputersimulationtopredictperformancehavebeendescribedinnumerousprevioustechnicalpapers.Manyoftheseinvestigatorshavebeenseeking,insomesense,thatelusivedesignwhichmightbetermedanoptimumsuspensionsystem.Thedifficultyassociatedwithobtaininganoptimaldesignisprimarilyduetothedifficultyofdeterminingtheoperatingenvironment（input）andarealisticfigureofmeritorcriterionforoptimization（output）.

Thefundamentalpurposeofavehiclesuspensionsystemistoactasavibrationisolationsystembetweentheframe,chassis,passengers,andcargo,andthevibratoryinputcausedbyroadorterrainirregularities.Thelackofafirmdeterministicdefinitionoftheprofiletowhichavehicleissubjectedthroughoutitslifetimerequiresastatisticalapproach,thatofrandomvibration.Theauthorandothers,forexample,havepreviouslymadesomeprogressinthestatisticaldefinitionoftheinput.Itappearsthatafairlyrealisticapproximationofroadorcross-countryterraincanbemadebyassumingawhite（equalprobabilityofallfrequencies）Gaussiandistributionfortheslope（orfirstspecialderivative）.Thiscanthenbeconvertedtoatemporalinputforvehiclevibrationstudiesbyaccountingforthespeedofthevehicleandtheinterrelationsassociatedwithfollowingin-linewheels.

Themeasureofthevibratoryresponseoroutputusuallyassociatedwithrandomvibrationismeansquareacceleration.Studieshaveindicatedthattheproperfrequencydomainweightingofmeansquareaccelerationtoaccountforhumanresonancescanyieldacriterionwhichcorrelateswiththesubjectivesensationofhumancomfort.Sinusoidalandrandomtestspecificationsforcomponentsandcargo,forexample,areusuallyassociatedwithaccelerationlevels.Fromthestandpointofcomponentfatiguefailurethereareindicationsthatarmsmeasurementofstresswillyieldarealisticcriterioninarandomenvironment.

Thus,itappearsthataproperlyidentifiedrandominputtogetherwiththeproperselectionofameansquareoutputmightbeusedasatechniqueforoptimizationoftrucksuspensionsystems.

Theauthorhasrecentlycompletedastudytodevelopsomeofthefundamentalrelationshipsnecessaryforoptimizationofvibrationisolationsystemssubjectedtorandominputsandthepracticalnumericaltechniquesrequired.Thispaperpresentssomeoftheresultsofthatstudyappliedtotheredesignofaparticulartrucksuspensionsystem.

OPTIMIZATION

Beforeexploringtheproceduresemployedtoachieveanimproveddesignofaspecificvehiclesuspensionsystem,itisofinteresttobrieflyexplorethemodernconceptsofoptimizationandsystemsanalysis.Fromanengineeringpointofview,thetechniquesemployedinthedesignofsystemscanbegroupedintotwoclassifications:

synthesisandanalysis.

Thesynthesisofasystemimpliesonlyaminimumamountofinformationaboutasystemandthenormaldefinitionisthatoftheinputandfunctionalrequirementsoroptimizationcriteria.Baseduponthisinformationthebestpossiblesystemissynthesizedtomeettheoptimalobjective.Fromthestandpointofsystemssubjectedtorandominputs,therudimentsofthesynthesistechniqueswerefirstintroducedbyWiener[9]andfurtherdevelopedbyNewton,Gould,andKaiser[10].AnapplicationofsynthesistechniquestovehiclesuspensionswaspresentedbyBender,Karnopp,andPaulin1967[1l].Thedifficultywiththistechniqueisthatitnormallyresultsinanactivesuspensionbaseduponservomechanisms.Carriedtotheextremethismightresultinahighlyelaborateservosystemincludingsurfaceprofilesensorstopredicttheexistenceofbumpspriortocontactandinitiateproperpreventiveaction.Whilethistypeofsuspensionsystemmaybeofinterestforsometypesofspecialpurposevehicles,andmayevenbecommonplaceinthefuture,itisnotpracticalforpresentcommercialormilitarytrucks.Thecostandcomplexity,theinherentmaintainabilityandreliabilityproblems,thedesiretoconserveweightandspaceforcargo,andotherlimitationsprecludetheuseofsynthesistechniquesinthecurrentstate-of-the-arttrucksuspensiondesign.Thepracticaluseofthesynthesisapproachistheestablishmentofanultimateoptimumlevelfortheperformanceofaparticularconfigurationinaparticularenvironmentwhichcanbeusedasabasisforthecomparisonofmorepracticalalternates.

Incontrasttothesynthesisapproachmoredefinitiveinformationisnecessaryfortheanalysisapproach.Normallythesystemconfigurationtogetherwithadescriptionoftheinputsandtheoutputcriteriaarerequiredinordertoperformanalysis.Aparametervariationisthenundertakentodeterminethesensitivityoftheoutputcriterionasafunctionofeachofthedesignparametersand/orcombinationsofdesignparameters.Withthisinformationanoptimalcombinationofdesignparametersissoughteitherthroughformaloptimizationprocedures[8]orthroughtrialanderrormethods.Theproceduresfortheapplicationoftheanalysisapproach,coupledwithlimitedfieldtesting,toimprovethesuspensiondesignofanexistingvehiclearedescribedintheremainderofthispaper.

PROCEDURE

Theproblemofinterestistheimprovementofthesuspensionsysteminaprototypetruck.Sincetheactualhardwarewasinexistence,inthiscase,theprocedureconsistedofactualfieldtestscoupledwithcomputersimulation.Instrumentedfieldtestswereundertakentoestablishabaselineandtocompareparametervariationsthatcouldeasilybeexploredinhardware.Theinstrumentationresultswereaugmentedbythesubjectiveimpressionsoftrainedsuspensionengineers.Amathematicalmodelofthetruckwasdevelopedsimultaneouslywiththefieldtesting,andresultswerecomparedtoestablishthevalidityofthemodel.Amathematicalparametersearchwasthenundertakentoseektheoptimumsuspensionparameters.Theresultsofthefield-testingandcomputersimulationwerethenusedtodesignanimprovedsuspensionforthetruck.

DESCRIPTIONOFTHEVEHICLE

ThevehiclewasalargemilitarytractorsemitrailercombinationcalledtheHeavyEquipmentTransporter（HET）.ThedevelopmentoftheHETconsistedofajointeffortbetweentheUnitedStatesandtheFederalRepublicofGermany.JointconceptstudieswereinitiatedinNovember1965bytheJointTaskForceconsistingofChryslerCorp.intheUnitedStates,andKruppandFauninGermany.Theresultofthesestudieswasaconceptconsistingofan8×8tractorandafour-axlesemitrailer.DuringthePhaseIIIDevelopmentContractwiththesamethreefirms,theconceptanddetaileddesignadvancedtothehardwarestatuswiththefabricationandassemblyofprototypevehicles.DifferencesinthenationalrequirementsresultedinvariationsbetweentheUnitedStatesandGermanversions.

ThevehicleofinterestistheUnitedStatesversionshowninFig.1withaM60A1E2MainBattleTankasapayload.ThreeUnitedStatesengineeringtestunitswereconstructedandeachtestedfor20,000milesofoperationoveracombinationofprimaryroads,secondaryroads,andcross-countryterrain.ThetrailerpassedalltestsandhasrecentlybeendesignatedtheM747.

Thetractor,theXM746,requiredmodificationsasaresultoftheengineeringtests.Whilethesuspensionsystemperformedadequatelyandtherewasnonecessityforchange,theopportunityaffordedbyotherdesignmodificationsresultedinaprogramtomodifythesuspensionforrideimprovement.Thustheinterestinthisprogramwasthatofminormodificationsinthetractorsuspensiononly.Thesuccessofthetrailersuspensiondictatednochangesinthatareaandthesuccessofthetractorhardwareprecludedmajormodificationswhichcouldresultinsubstantialrequalificationofaradicallydifferentsuspensiondesign.TwoadditionalAdvancedProductionEngineering（APE）tractorsweredesignedandconstructed.Oneofthese,theAPE-l,wasusedforthetestprogramattheU.S.ArmyAberdeenProvingGroundGrounds.TheHETtractor-semitrailercombinationhasanoveralllengthof732in.,anoverallwidthof137in.reducibletoabout120in.,andanoverallheightof119in.Thecombinationcurbweightis77,400lb,anditisdesignedforapayloadofI05,000lb,resultinginagrossvehicleweightof182,400lb.Theaxleloadsinthefullyloadedconditionarebelow25,000lb.Thevehicleispoweredbya600SAEh.p.dieselenginewhichgivesanenginegovernedtopspeedof38.5m.p.h.Thevehiclecanfordupto5ftwithoutpreparationandnegotiatea31.5%rampwithfullpayload.Thevehiclehasa26-ftlongflatcargodeckwithroomforanytrackedvehicleaswellaswheeledvehiclesorgeneralcargo.

The600h.p.dieselengineiscoupledtoapowershiftconverter-typetransmissionandatransfercase.Allfouraxlesaredriven,andnumbers1and2alsosteer.Thetractorhasanoveralllengthof332in.Thesuspension,showninFig.2,isaspringandlinkversionwith18×22.5,20plyratingtires.Eachsetofaxles,1and2,and3and4,formabogiearrangement.Theaxlesineachsetareinterconnectedwithalongitudinaltaperleafspringoneachsideofthevehiclewhichisfreetopivotatthecenterframeattachmentpoint.Eachaxleisseparatelyconstrainedbyaparallelogramlinkarrangement.Theendsofthespringarefreetoslidelongitudinallyinblocksprovidedineachaxle.Theonlydampingistheinherentfriction,andnoshockswereprovidedintheoriginalAPE-1vehicle.Heavy-dutypowersteeringisprovidedwithanaxle-dr